A known technique conventionally adopted for a treatment of an eye affected by cataract is to place an intraocular lens in a lens capsule after removal of a clouded nucleus of a crystalline lens (“lens”). For removal of cataractous nucleus of lens, phacoemulsification is used. In cataract operations, the nucleus of lens is emulsified and suctioned to be removed by an ultrasonic tip of a surgical appliance inserted in the lens capsule. The lens is coupled with a ciliary body by the Zinn's zonule. The zonule is composed of a countless number of fibrous tissues which are transparent and very thin. During the cataract operation, the lens is subject to an external force applied by movement of and suctioning by the ultrasonic tip, and a stress accordingly acts on the zonule in a manner that follows the movement of the lens. In the case where the zonule of an eye operated on is weak, the removal of the nucleus of lens involves a risk of complications caused by, for example, dislocation of the lens, and accidental drop of the dislocated lens in a vitreous chamber. Patent Document 1 discloses an operation for an eye with weak zonule.